1. Field of the Invention
This invention relates to an improved fuel injection valve for an internal combustion engine.
2. Description of the Prior Art
Known injection valves that are used for direct fuel injection into the combustion chamber of an internal combustion engine are generally provided with several injection openings, but are at least provided with one injection opening. The fuel injection valves control the injection of compressed and therefore pressurized fuel by the longitudinal movement of a valve needle that has a valve sealing surface and cooperates with a body seat. A distinction is drawn here between essentially two basic types: on the one hand, there are the so-called valve covered orifice nozzles in which the injection openings lead directly from a conical body seat and on the other hand, there are the so-called blind hole nozzles in which the injection openings lead from a blind hole. The blind hole nozzles have the advantage over valve covered orifice nozzles that the distribution of fuel to the individual injection openings occurs in a uniform fashion, generally achieving a more uniform injection pattern than in valve covered orifice nozzles. In blind hole nozzles, however, the problem arises that the fuel that travels between the valve sealing surface and the body seat is subjected to turbulence as it transitions into the blind hole, thus reducing the effective injection pressure at the injection openings.
DE 36 05 082 A1 has disclosed a fuel injection valve that functions in accordance with the principle of the blind hole nozzle. In this case, the valve needle is provided with a needle tip that protrudes into the blind hole even in the open position of the valve needle, i.e. when the needle has lifted away from the body seat. The needle tip has a conical sealing surface with which the valve needle rests against the body seat. This sealing surface is adjoined by a convex, i.e. outwardly arched, region, which, in turn transitions into a concave, i.e. inwardly arched, region. The end of the valve needle thus constitutes a dome that is also arched outward and tangentially adjoins the concave region. This shape of the valve sealing surface is supposed to deflect the fuel flow into the blind hole without causing it to detach from the needle tip in order to avoid turbulence. But in his case, the disadvantage arises that the form of the needle tip cannot be adapted equally well to all injection ports since as a rule, they enclose various angles with the longitudinal axis of the valve needle. This results in an optimized entry for only some ports, while the surface flow travels into other injection openings in a rather unfavorable fashion.